Science

Ruled by Sun and Moon

¡Viva la Science!

Take a look at the sky. See a big ball of light? If so, it’s probably doing something to you right now. Humans respond to light from the sun and the full moon in measurable ways, two new studies report, and our sleep hangs in the balance.

In one study, a bunch of lucky volunteers went camping in Colorado’s Rocky Mountains for a week. (For SCIENCE!) Before they went, they’d spent some time wearing activity monitors on their wrists. The monitors measured stuff like average activity levels, sleep duration and waking/sleeping times. After a week of monitoring, researchers used a saliva test to measure participants’ melatonin and determine their “natural” circadian rhythms.

During the camping trip, anything except natural light was verboten. No phones, no flashlights, just sunlight and campfires. After their wilderness adventure, during which they slept and woke when they wanted to, participants went back to the lab for more testing. Since all those measurements had been taken earlier, the researchers could see what had changed.

The main difference was in the amount of light individuals were exposed to: Study participants got four times as much of the stuff when camping. A thing to know about melatonin is that it normally rises in the early evening near sunset (to encourage sleep) and drops off in the morning before waking. For many of us, though, a life surrounded by the comforting glow of technology means that we’re getting artificial light at all hours of the day and night—and our melatonin levels reflect it, increasing later in the evening and sometimes not decreasing until after we’ve woken.

The campers’ melatonin levels after their trip, however, rose and fell according to the normal rhythm, chilling out at sunrise and ramping up at sunset. Participants’ circadian clocks shifted two hours earlier on average, indicating that time spent camping—or exposed to natural light—can “reset” the clock and help people fall asleep and wake up more easily.

Those are some pretty dramatic results, and they point to actions you can take if you want to adjust your own circadian rhythms. For example, you might try getting more natural light during the day. In the case of the moon, however, the measurable effect is more subtle and the plan of action isn’t so obvious.

*L*u*z*a* via Flickr

The moon study analyzed sleep data acquired from a previous study in a controlled laboratory setting. It looked at what phase of the moon the sleep data was associated with and found—much to the surprise of researchers—that a distinct pattern emerged. Despite volunteers being unable to actually see the moon in their laboratory bedrooms, their sleep was affected if it fell on a night near a full moon. Sleepers took five extra minutes, on average, to zonk out, plus they got shallower sleep and about 20 minutes less of it.

Do we have an internal clock that responds to cycles of the moon, just like we do for the sun? Maybe. Researchers really can’t say at this early point; this is “the first reliable evidence” that the moon can affect our sleep under laboratory conditions, they note.

Astrology this ain’t.These studies are small—only 8 people in the solar study and 33 people in the lunar—and additional research with larger groups and in other locations globally is needed if we want to draw firm conclusions. Nonetheless, this is science functioning precisely as science is supposed to. In both studies, we have a testable hypothesis, an experiment whose parameters can be repeated and results that can be impartially measured. Damn right, you should be excited.